---
layout: example.html
title: Tracing around a polygon
shortdesc: Using the draw interaction to trace around features.
docs: >
  The draw interaction has a <code>trace</code> option to enable tracing
  around existing features.  This example uses the <code>traceSource</code> option
  to trace features from one source and add them to another source.  The first click
  on an edge of the target feature will start tracing.  The second click on the edge
  will stop tracing.
tags: "draw, trace, vector, snap, topology"
---
<div id="map" class="map"></div>
<form>
  <label for="type">Geometry type &nbsp;</label>
  <select id="type">
    <option value="Polygon">Polygon</option>
    <option value="LineString">LineString</option>
    <option value="None">None</option>
  </select>
</form>
